Among the steps for manufacturing semiconductors there is a step, in order to miniaturize a semiconductor chip, in which a rear surface of a semiconductor wafer (hereinafter, referred to as a wafer) is ground to thin the wafer (back grinding step). In this back grinding step, a protection sheet made of an adhesive sheet and the like is adhered to the front surface (the surface on which the circuit is formed) of the wafer, thereby protecting the surface. Then, after the back grinding step, there is performed a processing in which the protection sheet is peeled off from the wafer.
The wafer that has been made ultrathin in the back grinding step is likely to be damaged even by the slightest shocks. Therefore, in order to prevent the wafer that has been made ultrathin from being damaged, at the time of transporting or machining, due to distortion by a self weight, acceleration, or processing stresses, there has been proposed a fixing jig which supports and fixes the wafer and which is made up of a plate-like jig main body; and a close contact layer which is provided on one surface of the jig main body and which detachably holds the work in close contact (see, e.g., patent document 1). This jig main body has on one surface a plurality of supporting projections which support thereon the close contact layer and also has, on an outer peripheral portion of said one surface, a side wall of substantially the same height as the supporting projections. The close contact layer is adhered to one end surface of the side wall. Between the close contact layer and the jig main body, there is defined a partitioned space which is enclosed by the side wall. The jig main body has formed therein a ventilation hole which is in communication with the partitioned space.
If the air within the partitioned space is sucked via the ventilation hole by evacuation of the ventilation hole, the close contact layer will be deformed so as to be dented at the position between the respective supporting projections. As a result, the area of contact of the wafer with the close contact layer will decrease. It follows that the wafer can be tumbled from the fixing jig without applying an undue force.    Patent Document 1: JP-A-2006-216775
However, when the processing is performed of peeling a protection sheet off from a wafer on which the protection sheet is adhered, if the above processing is performed the wafer fixed to the above fixing jig, the force to be applied to the wafer at the time of processing is partially strong. Therefore, the wafer will easily be tumbled from the fixing jig. In addition, in case the kind of the close contact layer is changed depending on the processing conditions so that the wafer does not drop, even if the partitioned space is reduced in pressure by evacuation of the ventilation hole, the close contact with the wafer will be so strong that the deformation of the close contact layer hardly takes place. As a result, when the wafer is removed from the fixing jig, undue force will be operated on the wafer and the wafer is likely to be broken.
In view of the above points, this invention has a problem of providing a fixing jig which can surely fix the work in close contact even when the processing of adding a force to the work is performed. This invention has also a problem of providing a method of processing a work by using the fixing jig.